I've came to the conclusion CO2 supplemntation grows plants 30% bigger and 30% faster. Don't use CO2 the last two weeks of flowering, it will prevent the plants from finishing.

Your dude should definetly get a tank and regulator or a CO2 generator, they have CO2 generators that run off natural gas or propane. The ones that run off natural gas are exellent because you can hook the up to the gas line in your house, so there is no worry about refilling tanks and what not.